Although bipolar disorder is the Axis I disorder associated with the highest risk of having a substance use disorder, little is known about the treatment of patients who are dually diagnosed with these two disorders. In particular, there have been no studies of behavioral treatment of this high-risk, poor-outcome patient population. The primary aim of this Phase one project is to develop a 12-session relapse prevention group therapy manual for patients with bipolar disorder and substance use disorder. This treatment manual will focus on practical themes that are relevant for both disorders; there will be an emphasis on educating patients about their two disorders, fostering manual support, discussing ambivalence about treatment, working on interpersonal relationships, and helping patients to accept their illnesses. The manual will combine therapist information and instructions with patient worksheets, handouts, and homework assignments. To accomplish this aim, the investigators will: a) Obtain outside review of the manual at two different stages of its development from experts in the treatment of bipolar disorder and substance use disorders. b) Develop and utilize a therapist "self-test" to help therapists identify their competence and readiness to use the material. c) obtain monthly assessment of subjects' substance use, psychiatric symptoms, treatment utilization, and medication compliance during treatment and for 3 months afterwards. These assessments along with data from a group of subjects receiving "treatment as usual," will help us to revise the manual. d) Establish the acceptability of the manualized treatment intervention by obtaining session-by-session and overall patient and therapist satisfaction ratings. e) Develop and refine therapist competence and adherence measures for the treatment intervention, and develop instructions for their use by raters. f) Revise the manual in an ongoing way, based on information from elements a-e above, while conducting the group intervention twice in the pre-pilot phase, and twice again during a pilot study. The investigators will then conduct a pilot study in which outcomes among subjects receiving the treatment intervention will be compared with outcomes of subjects who receive "treatment as usual."